For example, Japanese Unexamined Patent Application Publication No. 2005-116738 (Patent Literature 1) discloses a technology as a power supply device that converts an alternating power voltage with high efficiency, so as to acquire a direct current used to feed an LED (Light Emitting Diode) load, which is driven by a constant current.
According to the technology disclosed by Japanese Unexamined Patent Application Publication No. 2005-116738 (Patent Literature 1), a control signal used in an LED current control circuit is monitored, and, if it is detected that a forward voltage drop across the LED is low, i.e., the LED is efficient and a voltage drop across an FET (Field Effect Transistor) is high, a supply voltage for the overall LED current control circuit is decreased to reduce a wasted power consumed by the FET, thereby realizing a power saving. However, there is a drawback such that costs of design and manufacture will increase caused by increase in the number of features and types of LED load or increase in the number of specifications and types of lighting device equipped with LED load and power supply thereof.
On the other hand, for example, a pamphlet of WO2009/133723 (Patent Literature 2) discloses a technology as a switching power supply device that can change a feature and a specification thereof, independent upon a change in hardware design such as circuit configuration and circuit element constants, and control parameter generation device that generates a control program of the switching power supply.
According to the technology disclosed by the pamphlet of WO2009/133723 (Patent Literature 2), it is easy to change a design in accordance with changes in source voltage, load, and the like, and it is possible to change specifications without need for changes in circuit elements. Especially, an assembly manufacturer can easily reflect a user's proprietary specification on a circuit, and a device manufacturer only has to produce the selfsame power supply devices, thereby enabling to reduce the costs of design and manufacture.